In-group bias refers to the tendency of individuals to favor and prioritize members of their own group, while discriminating against or devaluing members of other groups. This phenomenon can occur at a variety of levels, including racial, ethnic, gender, and nationality-based groups, as well as more subtle distinctions such as political affiliations or personal interests.

One key factor contributing to in-group bias is the human desire for social belonging and the need to feel part of a larger community. This can lead people to identify more closely with their own group and to view members of other groups as "others," leading to a sense of competition or hostility.

Another factor contributing to in-group bias is the confirmation bias, in which people actively seek out information that confirms their preexisting beliefs and assumptions, while ignoring or dismissing evidence that challenges them. This can lead to a self-reinforcing cycle, in which people continue to believe in the superiority of their own group even in the face of contradictory evidence.

In-group bias can have significant consequences, including discrimination, segregation, and conflict. It can also lead to flawed decision-making and missed opportunities, as people may overlook or disregard the perspectives and contributions of members of other groups.